The present invention relates to gas turbine engines and, more particularly, to reduction of noise emanating therefrom.
In recent years, noise generated by flying aircraft has attracted attention and is now subject of various governmental regulations. Efforts need to be made to minimize annoyance to neighborhoods located in the path of departing and landing aircraft. The noise is especially disturbing during certain flight conditions such as takeoffs and landings of the aircraft.
The aircraft noise is primarily generated by gas turbine engines propelling the aircraft. One major source of the noise generated by the gas turbine engine is the fan section. The fan generates tonal and broadband acoustic energy propagating outward of the engine through an inlet and through a bypass nozzle.
Various considerations dictate design of the gas turbine engine that propels an aircraft. For example, several critical concerns are thrust of the engine, fuel efficiency, cooling, and the overall weight. Frequently, optimization of one factor results in undesirable consequences for another. Therefore, design of an engine includes multiple trade-offs to obtain an optimal engine. Although noise generated by the gas turbine engine is now subject to fairly stringent governmental regulations, to date, the noise considerations were not part of the design optimization for conventional engines.